March 5, 2013 -- A new study adds yet more evidence that the decline in physical activity is contributing to the rise in obesity in the U.S. This study, however, is bound to cause some controversy, as researchers found the increase in obesity in women is tied to a falloff in the amount of housework they currently do compared with days gone by.
Published in PLoS One, the study shows that women were doing far less housework in 2010 than they were in 1965, and this has led to burning about 360 less calories per day. In 1965, women cooked, cleaned, and did laundry, among other household work, an average of 26 hours per week. In 2010, the amount of time spent doing the same work declined to 13 hours per week.
The researchers stress, though, that they are not suggesting women, or men, do more housework. Instead, the results should get people to think about how much energy they use throughout the day and also get policymakers to think about addressing the "calories out" aspect of obesity and the energy equation.
"Our results show that we have engineered physical activity out of the workplace, out of the home, and out of our daily commute," says researcher Edward Archer, MD, of the University of South Carolina in Columbia, "and this has severe and dramatic consequences for our health. We need to find a way of reintegrating that activity to make up for the [decrease] in calories expended."
Calories In, Calories Out
The researchers used historical data to get a better idea of the amount of time spent on specific activities in the past. They found that the time spent doing housework declined from 25.7 hours per week in 1965 to 13.3 hours per week in 2010, with non-employed women cutting the amount of weekly housework by nearly 17 hours and working women by nearly seven hours.
The amount of energy used in household management declined 42% for non-employed women, down from 6,004 calories burned per week in 1965 to 3,486 calories burned per week in 2010 -- a weekly reduction of 2,518 calories.
"We found that non-employed women are spending about 360 calories less per day in physical activity, and if we look at obesity as calories in and calories out, this is a huge number of calories," Archer says. "It's about 15% of their total daily energy expenditure. We spend hundreds of millions of dollars studying diet and nutrition, which is the energy in, but we spend almost no money on the energy-expenditure portion of the equation. The most modifiable factor in the energy-balance equation is physical activity."
The researchers also found that the amount of time women spent watching television, and later using the computer, doubled from eight hours in 1965 to 16 hours in 2010.
Archer says the physical activity guidelines for health recommend 30 minutes per day, which is enough to lessen the risk of heart disease and stroke. However, this is not going to have much of an effect on weight and body fat. For that, the Institute of Medicine recommends at least an hour per day of moderate activity for weight maintenance, and at least 90 minutes to two hours of daily moderate exercise to lose weight.
Archer says that while patients complain they are not going to have enough time for that, he says the television is the biggest source of wasted time.
"The number one recommendation is to turn off the television and replace that time with walking and lifting weights," he says.
To see a version of this story for physicians, visit Medscape, the leading site for physicians and health care professionals.